正交各向异性岩体中非圆形水工隧洞的解析解

将围岩和衬砌分别视作均质、连续的线弹性正交各向异性和各向同性体,并充分考虑衬砌的支护滞后效应和隧洞运行时的内水压力作用,运用复变函数方法中的幂级数解法,提出了正交各向异性岩体中任意形状水工隧洞的力学解析方法。以直墙半圆拱形水工隧洞为例,所获得的解析解可精确满足衬砌内边界的应力边界条件以及围岩与衬砌接触面的应力、位移连续条件,同时还将解析结果与ANSYS数值结果对比分析,吻合良好。利用获得的解析解,讨论了围岩开挖面上不同的各向异性程度、不同的弹性对称面角度以及隧洞内不同的水压荷载对衬砌以及围岩上应力和位移分布的影响。     

Design of tunnel linings in a creeping rock

Summary The effect of long term rock deformation on lining pressure is considered using different concepts of rock behaviour. These include the conventional characteristic-line or convergence-confinement method, modified to allow for rock ageing, and lining-rock interaction methods using models of linear-viscoelastic, linear-elastic linear viscous, and linear elastic non-linear viscous rock behaviour. Calculations of lining pressures show that the former tends to underestimate, compared with the latter.This paper was presented at the 28th US Symposium on Rock Mechanics in Tucson, Arizona, July 1987.     

Analysis of fracture propagation in a rock mass surrounding a tunnel under high internal pressure by the element-free Galerkin method

Fractures developed around high pressurized gas or air storage tunnels can progressively extend to the ground surface, eventually leading to an uplift failure. A tool reasonably reproducing the failure patterns is necessary for stability assessment. In this study, a numerical method based on the element-free Galerkin (EFG) method with a cohesive crack model is developed to simulate fracture propagation patterns in the rock mass around a tunnel under high internal pressure. A series of physical model tests was also conducted to validate the reliability of the developed method. A qualitative agreement between physical model tests and numerical results can be obtained. The in situ stress ratio, k, has a strong influence on both the position of crack initiation and the propagation direction. The numerical analyses were extended to full-scale problems. Numerical tests were performed to investigate the prime influencing factors on the failure patterns of a high pressurized gas circular tunnel with varying parameters. The results suggest that initial in situ stress conditions with a high k (larger than 1) is favorable for construction of pressurized gas or air storage tunnels.     

横观各向同性岩体中马蹄形隧洞的位移反分析方法

将各向异性岩体中任意形状隧洞的位移解析解与智能算法--差分进化法（DE）结合,研究横观各向同性岩体中在各向异性面上开挖马蹄形隧洞的位移反分析问题,获得关于参数灵敏度、参数可惟一辨识性和测线布置方案的有关结论。计算发现,通过DE算法可获得很高精度的参数辨识结果;参数的可惟一辨识性不仅与灵敏度有关,还与具体的参数组合形式有关,在给定竖向地应力和各向同性面角度的情况下最多可以高精度惟一辨识5个参数;当待辨识参数的个数大于等于4时会产生不可完全高精度惟一辨识的参数组合,当待辨识参数的个数小于等于3时,任意的参数组合形式均可以被高精度惟一辨识。     

常用围岩分类方法对某深埋隧洞的适用性分析

某深埋隧洞局部地应力高达42 MPa,局部外水压力高达10 MPa,具有高地应力、高外水压力的特点。一般认为,最大主应力大于20 MPa属于高地应力,外水压力远大于1 MPa为高外水压力。采用Q系统、RMR分类、水电规范HC分类、国标BQ分类等4种常用围岩分类方法对该隧洞进行了围岩分类。分类结果表明,高地应力条件下,Q系统的适用性较好,RMR分类、HC分类、BQ分类适用性均差。4种分类方法在高外水压力条件下的适用性均差。出现上述现象的主要原因有:Q系统通过最大切向应力与岩石抗压强度的比值σθ/σc的大小,反映高地应力对围岩类别的影响。故其在高地应力条件下的适用性较好;RMR分类没有考虑高地应力对围岩类别的影响。其分类结果在高地应力区特别是岩爆段偏高;HC分类在高地应力区简单地采用降级的方法。其分类结果误差较大;BQ分类对岩石强度过于敏感。其分类结果在高地应力区过于保守。这4种方法均未考虑高外水压力对围岩类别的影响。论文提出了一种“归一化方法”,可以对不同分类方法分类结果进行相互比较。     

Displacement analysis of tunnel support in soft rock around a shallow highway tunnel at Golovec

Within the last 10 years Slovenia has been constructing its highway network. The Golovec tunnel, as a part of Slovenia's capital ring is thus one of the most important connections of Ljubljana to the east and to the north. It is a double tube three-lane tunnel in soft rock with small to medium overburden. Its construction, following NATM, caused huge problems to all parties involved. The tunnel support was well monitored during its construction, which gave the authors a good opportunity to analyse the results.The Golovec tunnel is constructed through one of few hills surrounding Ljubljana, of Carboniferous age, consisting of clastic rock: siltstone, claystone and sandstone. Golovec hill belongs to the first of two overthrusting zones from this area, so the rock is strongly faulted.Tunnel monitoring consisted of daily 3-D tunnel tube displacement measurements in 97 measuring sections, and of two measuring sections within the tunnel with more complex measuring equipment, to monitor stress changes and rock deformations around both tunnel tubes. Monitoring of the surface 3-D movements gave us the opportunity to study the influence of the tunnel construction on the surface above it. The tunnel, its geology, construction procedure and monitoring results are described in the first part of the paper.The second part consists of the interpretation of monitored results, with an emphasis on results concerning development and evolution of the excavation-damaged zone in the rock around the tunnel. Back-calculations, performed as a basis for the interpretation procedure, are also presented in this part. Calculations of the propagation of the tunnel destressed zone and stress-field around the tunnel, up to the surface, were performed by means of numerical model with the finite difference method. The evolution of tunnel displacements and their prediction was based on the use of Back Propagation Neural Networks, whose principles are presented in one chapter of this paper. Results showed that the most important, for the final settlement at the surface above the tunnel, was the time of installation and rigidity of the primary support. On the basis of the calculated final displacements, this support could easily be strengthened in a short time, when necessary.     

Analytical solutions for nonlinear consolidation of soft soil around a shield tunnel with idealized sealing linings

This paper presents the analytical solutions for nonlinear consolidation of soft soil around a shield tunnel with idealized sealing linings. By introducing the empirical relation between permeability and compressibility, along with the conformal transformation, the governing equations of nonlinear consolidation are established, and the corresponding analytical solutions are derived. Then, the Terzaghi consolidation solutions are derived from the degenerate governing equation of nonlinear consolidation. Through the predictions of different consolidation theories in both completely permeable and impermeable lining conditions, the influences of a tunnel acting as a drain and impacting the dissipation of pore pressure, degree of consolidation, long-term ground settlements and ground settlement rates are investigated. During the early stages of consolidation, the case studies reveal that the predictions made by this study strongly agree with the field data when a completely permeable lining is applied. This study confirms that a tunnel acting as a drain can accelerate the consolidation of soil and enlarge soil deformation due to consolidation. During long term consolidation, a notable nonlinearity of the soil consolidation is exhibited by a small and gradually decreasing settlement rate, showing agreement with the tendency of field data from the impermeable conditions.     

Probabilistic assessment of tunnel convergence considering spatial variability in rock mass properties using interpolated autocorrelation and response surface method

This study aims at the probabilistic assessment of tunnel convergence considering the spatial variability in rock mass properties. The method of interpolated autocorrelation combined with finite difference analysis is adopted to model the spatial variability of rock mass properties. An iterative procedure using the first-order reliability method(FORM) and response surface method(RSM) is employed to compute the reliability index and its corresponding design point. The results indicate that the spatial variability considerably affects the computed reliability index. The probability of failure could be noticeably overestimated in the case where the spatial variability is neglected. The vertical scale of fluctuation has a much higher effect on the probabilistic result with respect to the tunnel convergence than the horizontal scale of fluctuation. And the influence of different spacing of control points on the computational accuracy is investigated.     

深部软弱岩体置换体对岩质边坡支护效果分析

大岗山水电站右岸边坡位于大渡河断裂和磨西断裂所切割的断块上,地震发生频繁且烈度高,岩体卸荷强烈,构造稳定性差,裂隙发育集中。已有研究成果显示出边坡开挖过程中锚索支护的重要性,也有较多学者对抗剪洞支护的设计进行了较全面的研究。在已有的锚索支护基础上,基于卸荷理论对设计抗剪洞的再次支护效果和和采用拟静力法模拟的抗震效果进行评估,通过不同高程的关键点的位移响应,较系统地论证抗剪洞设置的必要性。通过研究应力的变化发现锚索支护段和抗剪洞支护段之间形成较为明显的拉裂区域。对工程后期监测提出建议。     

引水隧洞膨胀性围岩的稳定性分析

膨胀岩在实际工程中通常表现为围岩随时间的推移大量向洞室内塑性挤出或底板大量隆起,最终导致洞室支护和围岩产生裂损或破坏。山西万家寨引黄入晋工程南干线7号隧洞地层特点除砂岩与泥岩互层外,膨胀岩共有3～4层,且斜穿隧道。通过对隧洞开挖及支护过程应用考虑膨胀岩影响的粘弹塑性有限元进行分析,得出膨胀围岩对隧洞及支护结构的受力及稳定性的影响。建议在通水运行过程中密切监测其变形、应力应变、渗透压及外水压力的变化规律,以确保工程的安全运行。     

大埋深高地应力关山隧道围岩变形破坏分析

甘肃省关山隧道是一条受高地应力影响的大埋深硬脆性闪长岩铁路隧道,位于青藏高原东北缘,构造活跃,运动速率较大,且方向变化显著的六盘山挤压隆升构造区。在隧道开挖过程中围岩变形破坏现象明显,围岩等级低于前期岩体质量分级,表现出强烈的岩体质量劣化和各向异性。针对该问题,除了采用矿物成分和微结构分析寻找原因,还通过现场结构面统计分析对围岩质量劣化和各向异性进行描述,同时运用自行研发的钻孔电视进一步分析开挖前后一定时间间隔内围岩的渐进式变形和破坏。钻孔电视试验结果表明,尽管闪长岩作为一种硬脆性岩体,单轴抗压强度（UCS）高于现场地应力值,但其变形和破坏却普遍发生,开挖过程中新生裂隙迅速发育,原先在高地应力下闭合的裂隙也会重新张开和发展,围岩劣化,稳定性降低。为了进一步分析围岩的变形破坏过程,设计了变压力大小和方向的单轴抗压试验,试验中闪长岩的单轴压力值低于单轴抗压强度,试验结果与钻孔电视试验观测结果吻合,证明了在开挖引起的地应力剧烈变化条件下硬脆性闪长岩结构劣化,存在变形破坏的可能性。在大埋深高地应力条件下,除了岩体的各向异性,地应力的变化也是硬脆性围岩稳定性的重要考量因素。     

结构面三维网络模拟在岩体质量评价中的应用

岩石质量指标RQD是反映工程岩体完整程度的定量参数,广泛用于水利水电、矿山、地下工程、交通工程等岩体稳定性评价,但是传统的RQD定义不能满足实际工程岩体各相异性要求。针对贵州黔中水利枢纽工程拱坝坝基岩体结构面特征,利用Monte-Carlo法在计算机上生成岩体节理三维网络图,建立了模拟计算不同阀值t的岩石质量指标RQDt的计算机模拟方法。该方法能较真实客观地描述岩石质量。     

坝区岩体蠕变参数解析-智能反演方法及其工程应用

岩体蠕变参数是岩土工程设计必不可少的重要资料,为准确确定岩体的蠕变力学参数,综合考虑解析反演法和智能反演法的优点,将这两种反演方法耦合,建立了岩体蠕变参数的解析-智能反演方法,将这种方法应用到大岗山水电站工程中,解析智能反演获得坝区岩体的压缩蠕变参数。计算结果表明：解析-智能反演蠕变曲线与试验蠕变曲线的拟合程度比解析反演蠕变曲线与试验蠕变曲线的拟合程度好,说明解析-智能反演法获得的坝区岩体蠕变参数更为准确可靠,同时也验证了这种参数反演方法的有效性和合理性。该方法为高效快捷地反演坝区岩体的蠕变参数提供了重要理论指导。     

岩体三维非稳定渗流模型及数值模拟

地下水是导致地质灾害发生的重要因素之一。岩体本身的复杂性及地下水在岩体内随时间而变化造成地下水在岩体内运动机理的复杂性。文章采用数值模拟方法探索地下水在岩体内的运动规律,了解其致灾机理。以岩体结构力学为基础,运用现代分形理论,建立主干裂隙分形网络;根据裂隙发育规模与工程尺度关系将岩体看作拟连续介质与块裂介质混合介质,并根据两类介质接触处水头相等及节点流量相等建立合理的三维非稳定渗流模型;给出渗流模型的有限元解法,开发出相应的有限元软件;给出算例,计算结果体现了主干裂隙在渗流中的强导水作用及网络状裂隙的贮水功能与渗流滞后效应;强调根据裂隙发育规模与工程尺度关系确定合理渗流模型的重要性。     

动荷载作用下隧道围岩块体稳定性分析及其应用

隧道围岩中的结构面将岩体切割成块体,块体在自然状态下的静力平衡因为隧道开挖而被打破,临空面的产生和动荷载的施加都可能导致块体的滑移,进而引起围岩失稳。以往应用块体理论寻找关键块体时,多只考虑纯重力的作用,而忽视了爆破振动、地震等动荷载对诱发失稳灾害的重要作用。将爆破振动荷载和地震荷载转化为等效静力,并通过数学计算求出使块体安全系数最低的动荷载方向,再利用关键块体理论矢量分析方法分析隧道围岩的稳定性。在长岗隧道中的应用表明,考虑动荷载作用下的块体安全系数明显小于只考虑重力作用时的安全系数,原本稳定的块体也可能在动荷载作用下变成关键块体导致围岩失稳,这与长岗隧道现场记录的破坏现象相符。     

块裂结构岩质边坡水力学模型及数值模拟

把块裂结构岩质边坡看作拟连续介质与块裂介质广义双重介质,运用现代分形理论,建立了1-2级主干裂隙分形网络,并根据两类介质接触处水头相等及节点流量相等建立了合理的块裂结构边坡三维水力学模型,给出了有限元解法,模拟了三峡工程的蓄水位至175 m时边坡渗流场与应力场的变化,在应用上有较好的可靠性与广泛性。     

基于统一强度理论深埋圆形隧道围岩的剪胀分析

基于连续介质理论中岩体的剪胀角与围压和塑性剪切应变密切相关,隧洞周边岩体的应力状态因开挖卸荷而发生应力重分布,迫使其围压由原地应力逐渐衰减,塑性剪切应变不断增加,引起剪胀效应呈非线性变化。首先,基于统一强度理论和非关联流动法则,将潜在塑性区围岩按等围压释放划分为若干同心圆,提出了考虑中间主应力和非线性剪胀性的有限差分法,计算应变软化围岩的力学问题,并以实例验证其正确性。其次,通过参数分析,研究塑性区内岩体的剪胀角受中间主应力、临界软化系数和支护力的影响规律。研究结果表明,中间主应力主要影响剪胀角的峰值,随着中间主应力效应增加,剪胀峰值增加;临界软化系数主要影响剪胀角的变化率,随着临界软化系数的增加,剪胀角变化缓慢;中间主应力和临界软化系数共同影响塑性区剪胀角的变化;随着支护力的增加,洞壁处的剪胀角增加;双剪强度理论计算的位移值较小,应谨慎采用,同时采用Mohr-Coulomb强度准则时可以适当考虑围岩的承载潜力。     

深隧道围岩稳定性的数值模拟与模型试验研究

在大型真三轴模型试验机上进行隧道的超载试验,试验过程中采用内窥摄影实时监测试件的破坏演化全过程,确定了高应力条件下隧道的变形特征和裂纹演化特征;采用应变测量技术对隧道关键部位的应变值进行了测量,据此分析了围岩体的应力变化规律。针对相似材料的力学特性,建立了应变软化模型,采用与模型试验相同的边界条件进行了数值模拟分析,对围岩体的塑性应变变化过程和应力场进行了研究。结果表明,两种手段反映的破坏演化过程是基本吻合的,所反映的围岩体应力变化规律也是一致的。     

损伤条件下深部岩体巷道光面爆破参数研究

岩体条件复杂多变,为了提高光面爆破的适应性、改善光面爆破效果,对损伤条件下深部岩体巷道光面爆破参数进行研究。通过对深部岩体巷道光爆层原岩应力场、光面爆破机制和振动损伤特征进行分析,基于爆炸应力波和爆生气体综合作用理论,考虑高原岩应力和岩石损伤影响,提出了损伤条件下深部岩体巷道光面爆破参数确定的计算方法。研究表明, （1）高原岩应力相当于提高了岩石的抗拉强度,不利于炮孔初始裂纹的形成及贯通,宜减小周边眼间距;（2）岩石损伤后,其他条件不变,光面爆破的炮孔间距和抵抗线值可适当加大;（3）高原岩应力和损伤条件下,光面爆破的炮孔间距较小时,容易造成爆后围岩损伤,降低围岩的稳定性能,因此,提高爆破效果的同时应及时加强支护,以确保施工安全和围岩稳定;（4）本文提出的光面爆破参数计算公式,经现场爆破验证效果良好,适用于复杂多变的岩体环境。